Hydrogen ion adsorption at the rutile-water interface to 250{degrees}C

Journal Article · Thu Dec 01 04:00:00 EST 1994 · Geochimica et Cosmochimica Acta

DOI:https://doi.org/10.1016/0016-7037(94)90254-2· OSTI ID:28815

Machesky, M L ^[1]; Palmer, D A; Wesolowski, D J ^[2]

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1. Illinois State Water Survey, Champaign, IL (United States)
2. Oak Ridge National Lab., TN (United States)

A stirred hydrogen-electrode concentration cell was used to follow hydrogen ion adsorption by the rutile surface in NaCl media (0.01-1.0 m) between 25 and 250{degrees}C. The pH of zero net surface charge (pHzpc) decreases to 200{degrees}C and then appears to increase. Away from the pHzpc, negative surface charge is screened more efficiently by Na{sup +} ions than positive charge is by Cl{sup {minus}} ions and this effect increases with temperature. Thus, Na{sup +} moves closer to the rutile surface with increasing temperature relative to Cl{sup {minus}}. Finally, [pHzpc - 1/2pK{sub w}] is approximately constant (-1.1 {+-} 0.2) for this rutile sample to 250{degrees}C and is also equivalent to the equilibrium constant for an isocoulombic form of the {open_quotes}1pKa{close_quotes} surface ionization model. Thus, the constancy of [pHzpc - 1/2pK{sub w}] may also be useful for extrapolating rutile pHzpc values to higher temperatures and pressures than those studied here, and may also apply to many other oxide surfaces as well.

• DOE Contract Number: AC05-84OR21400
• OSTI ID: 28815
• Journal Information: Geochimica et Cosmochimica Acta, Journal Name: Geochimica et Cosmochimica Acta Journal Issue: 24 Vol. 58; ISSN GCACAK; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
58 GEOSCIENCES
ADSORPTION
HYDROGEN IONS
PH VALUE
ROCK-FLUID INTERACTIONS
RUTILE
SODIUM CHLORIDES
SURFACE IONIZATION
TEMPERATURE DEPENDENCE